• Manjunath B Bellakki

      Articles written in Bulletin of Materials Science

    • Solution-combustion synthesis of Bi1–𝑥Ln𝑥O1.5 (Ln = Y and La–Yb) oxide ion conductors

      Manjunath B Bellakki A S Prakash C Shivakumara M S Hegde A K Shukla

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      Cubic fluorite related Bi1–𝑥Ln𝑥O1.5 (Ln = Y and La–Yb) phases are synthesized by solutioncombustion method using glycine as the fuel. The cubic fluorite phase is stabilized with 25 mole% of rare earth cations. The lattice parameter of cubic phase increases linearly with size of the lanthanide ion. The synthesized powders are nano-metric in size and exhibit excellent compactability and reach 98% densification even on short period of sintering. The oxides with relatively larger cations Nd, Sm, Eu, Pr and Gd with 25 mole% composition transform to rhombohedral structure while others retain cubic upon sintering. All the phases show high oxide–ion conductivity and the values obtained are in good agreement with the reported values.

    • Synthesis, structural and ferromagnetic properties of La1–𝑥K𝑥MnO3 (0.0≤ 𝑥 0.25) phases by solution combustion method

      C Shivakumara Manjunath B Bellakki

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      We describe the solution combustion synthesis and characterization of La1–𝑥K𝑥MnO3 (0.0 ≤ 𝑥 ≤ 0.25) perovskite phases, which is a low temperature initiated, rapid route to prepare metal oxides. As-synthesized compounds are amorphous in nature; crystallinity was observed on heating at 800°C for 5 min. Structural parameters were determined by the Rietveld refinement method using powder XRD data. Parent LaMnO3 compound crystallizes in the orthorhombic structure (space group 𝑃𝑏𝑛𝑚, No. 62). Potassium substituted compounds were crystallized with rhombohedral symmetry (space group 𝑅–3c, No. 167). The ratio of the Mn3+/Mn4+ was determined by the iodometric titration. The Fourier transform infrared spectrum (FT–IR) shows two absorption bands for Mn–O stretching vibration (𝜈s mode), Mn–O–Mn deformation vibration (𝜈b mode) around 600 cm-1 and 400 cm-1 for the compositions, 𝑥 = 0.0, 0.05 and 0.10. Four-probe electrical resistivity measurements reveal a composition controlled metal to insulator transition (𝑇M–I}}$), the maximum 𝑇M–I was observed for the composition La0.85K0.15MnO3 at 287 K. Room temperature vibrating sample magnetometer data indicate that for the composition up to 𝑥 = 0.10, the compounds are paramagnetic whereas composition with 𝑥 = 0.15, 0.20 and 0.25 show magnetic moments of 27, 29 and 30 emu/g, respectively.

    • Solution combustion synthesis of (La, K) FeO3 orthoferrite ceramics: structural and magnetic property studies

      Manjunath B Bellakki V Manivannan

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      Polycrystalline La1–𝑥K𝑥FeO3 ceramic oxides were synthesized by a solution combustion process using glycine as a fuel. The synthesized ceramic powders were characterized for structural features applying characterization techniques such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and magnetic and optical property studies applying characterization techniques such as SQUID magnetometer and diffuse reflectance (DR). The changes in magnetic properties are correlated to changes in structural features resulting from Rietveld structural refinement.

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